1. Field of the Invention
This invention relates to a technique for quantization of images. This invention especially relates to a method and apparatus for image quantization, and an apparatus for coding images using the quantization method.
2. Description of the Related Art
In recent years digital image culture has become commonplace in our daily life as various information devices such as personal computers, digital cameras and color printers have been introduced into our homes and the number of Internet users has exploded. Image compression technology such as JPEG (Joint Photographic Expert Group) and MPEG (Motion Picture Expert Group) for still images and motion images respectively has been standardized. Image distribution and reproduction have become easy and convenient for users using recording media such as CD-ROM and transmission media such as networks and broadcasting technology based on the aforementioned image compression technology. JPEG 2000 has been announced in the JPEG line of technology. In MPEG also, future target specifications have been planned and discussed. There is no doubt that image processing technology will soon play an important role in improving the functionality of digital devices.
In the field of digital camera, for example, so-called mega-pixel cameras are a mainstream item in the consumer market. Demand for improved image quality seems endless. However, more processing time and power are required to handle images of finer quality.